It’s also an exam many people dread. The test itself is brief, and most people are under general anesthesia during it. You won’t feel or see anything, and recovery generally takes only a few hours. Preparing for the exam, however, can be unpleasant.

That’s because your colon needs to be empty and clear of waste. This requires a series of strong laxatives to clean your intestines in the hours prior to the procedure. You’ll need to stay in a bathroom for several hours, and you’ll likely deal with some uncomfortable side effects, like diarrhea.

When your doctor requests the colonoscopy, they’ll provide you with information on how to prepare for it, what products to use, and what you can expect. This information will likely break down what you need to do by the day.

Although the timeline below can give you a general understanding of the process, your doctor is your best resource if you have any questions or concerns.

7 days before: Stock up

Get a head start on your preparations and head to the store at least a week before your colonoscopy. Here’s what you’ll need:

Laxatives

Some doctors still prescribe laxative medication. Others recommend a combination of over-the-counter (OTC) products. Buy the products your doctor recommends, and if you have any questions, call your doctor’s office before the day you’re meant to prep.

Moist wipes

Regular toilet paper may be too harsh after several trips to the bathroom. Look for moist or medicated wipes, or wipes with aloe and vitamin E. These products contain ingredients that can soothe irritated skin.

Diaper cream

Before your prep starts, cover your rectum with a diaper cream like Desitin. Reapply throughout the prep. This will help prevent skin irritation from the diarrhea and wiping.

Approved foods and sports drinks

The week of your colonoscopy, you’re going to eat foods that are easier to pass and less likely to cause constipation. Stock up on those now.

They include:

low-fiber foods

sports drinks

clear fruit juices

broths

gelatin

frozen pops

You’ll need at least 64 ounces of a drink to take your laxative, so plan accordingly. Sports drinks or light-colored, flavored beverages can help make taking the medication easier.

5 days before: Adjust your diet

At this time, you should start adjusting your diet to include foods that are easier to pass through your digestive system.

Low-fiber foods

Switch to low-fiber foods at least five days before your exam. Some options include:

white bread

pasta

rice

eggs

lean meats like chicken and fish

well-cooked veggies without the skin

fruit without skin or seeds.

Soft foods

Switching to a soft-food diet at least 48 hours before the colonoscopy may make your preparation easier. Soft foods include:

scrambled eggs

smoothies

vegetable purees and soups

soft fruits, like bananas

Foods to avoid

During this time, you also need to avoid foods that can be hard to digest or get in the way of the camera during your colonoscopy. These include:

fatty, fried foods

tough meats

whole grains

seeds, nuts, and grains

popcorn

raw vegetables

vegetable skins

fruit with seeds or skins

broccoli, cabbage, or lettuce

corn

beans and peas

Medications

Ask your doctor whether you should continue to take any prescription medications during your prep or if you should stop until after the procedure. Be sure to also ask about any vitamins, supplements, or OTC medications you use daily.

24 hours before

No matter your diet in the days before your colonoscopy, you must switch to a liquid-only diet 24 hours before your exam. That’s because your body needs time to eliminate waste from your colon so the colonoscopy is a success.

If the colon isn’t clear, your doctor may have to reschedule the appointment for a later date. That means you’ll need to prep again in the future.

It’s important you stay hydrated during this time. You can eat and drink any clear liquids you want, but a good rule of thumb to follow is eight ounces per hour that you’re awake. Chug a glass of water or sports drink every hour, and you shouldn’t have any issues.

The night before

It’s time to begin cleaning out your colon of any remaining waste. To do this, your doctor will prescribe a strong laxative.

Most doctors now recommend a split dose of laxatives: You take half the mixture the evening before your exam, and you finish the second half six hours before your exam. You may also take pills at the beginning of the process.

If your exam is early in the morning, you may begin the process 12 hours before you’re scheduled to start your colonoscopy and finish the dose before midnight.

The laxative may be difficult to swallow because of a bitter taste. Try these techniques to make it easier:

Mix it with a sports drink. Flavored drinks can cover any unpleasant tastes.

Chill it. Mix the drink and laxative 24 hours before you’re set to begin the prep. Refrigerate it so the drinks are cold. Chilled drinks are sometimes easier to swallow.

Use a straw. Place the straw at the back of your throat where you’re less likely to taste it when swallowing.

Chase it. Squeeze a bit of lemon or lime juice in your mouth after you drink the laxative to kill the taste. You can also use hard candy.

Add flavorings. Ginger, lime, and other aromatics add a lot of flavor to liquids. That may make drinking the laxative more pleasant.

Once you take the laxative, your intestines will begin pushing out any remaining waste very quickly. This will cause frequent, forceful diarrhea. It can also cause:

2 hours before

Don’t drink anything — even water — two hours before your procedure. This step is important to help prevent you from getting sick after the procedure. People who drink right before the procedure risk getting sick and breathing vomit into their lungs. Some hospitals request a longer window without liquids, so follow their instructions.

The bottom line

The prep for a colonoscopy, as well as the recovery, may be uncomfortable and inconvenient. However, the alternative — not finding and diagnosing potential problems, including colon cancer — is much worse.

Be sure to follow any directions your doctor provides, and don’t be afraid to ask if you have any questions. It’s also worth noting that if your colonoscopy is successful, you may not need another one for 10 years.